1. Field of the Invention
The present invention relates to a navigation device for displaying a current position of a vehicle, and particularly to a navigation device for displaying a current position of a vehicle by being superposed on a map which is stereoscopically displayed.
2. Description of Related Art
Conventionally, there has been known a navigation device for facilitating driving of an automobile. According to the navigation device, digital map data recorded in a record medium such as CD-ROM or the like is read, a map is displayed on a screen of a display device such as a liquid crystal display or the like and the current position of a vehicle (position of a driving car) that is detected by a position measuring system of a GPS (Global Positioning System) receiving device or the like is overlappingly displayed. Further, a route from the current position to a target location is displayed and the vehicle is guided along that route.
According to a such a navigation device, it is normal to display a planar map (two-dimensional map) on a screen. However, there also is a navigation device for displaying a quasi three-dimensional map to further promote visibility. The method of displaying a quasi three-dimensional map is referred to as "quasi three-dimensional display" in which a perspective view (bird's eye view), that is obtained when a driving vehicle is viewed from an observing point set at a predetermined position in the sky above the driving vehicle in a direction forming an acute angle with respect of the ground, is formed based on map data representing a two-dimensional map and a perspective view is displayed in a display device. In this way, depth perception is given to an operator.
Meanwhile, in displaying the position of a driving vehicle on a screen, there is a case where processing referred to as map matching is also used. Map matching is processing for correcting the position of a driving vehicle detected by a position measuring system based on road coordinates obtained from map data read from a record medium. By also using the map matching, extreme departure of the position of a driving vehicle from a road displayed on a screen can be prevented.